The present invention generally relates to high density signal recording and reproducing apparatuses, and more particularly to a recording and reproducing apparatus which records and reproduces a digital signal on and from a recording medium such as a floppy disk and a Winchester disc with a high density by use of an existing recording format.
Recently, floppy discs such as the 8-inch and 5.25-inch discs are used as recording mediums for personal computers and office computers. When the usable range (maximum usable radius minus minimum usable radius) of the disc is represented by F inch and the track density is represented by D track/inch, the usable number A of tracks on one side of the disc can be obtained by the following equation (1). EQU A=(F/D)+1 (tracks) (1)
When the memory capacity per track is represented by B bytes, the total memory capacity M on one side of the disc can be obtained by the following equation (2). EQU M=B.times.A (bytes) (2)
A standard format is set for a floppy disc drive which plays the floppy disc, and the digital signal is recorded on the disc with a predetermined recording format. For example, the memory capacity B per track (format capacity per track) of the 3.5-inch and 5.25-inch discs is approximately equal to 4 kilobytes, and the memory capacity B per track of the 8-inch disc is approximately equal to 6.6 kilobytes. In addition, the data transfer speed S of the 3.5-inch and 5.25-inch discs is approximately equal to 250 kilobits/second, and the data transfer speed S of the 8-inch disc is approximately equal to 500 kilobits/second, for example.
The memory capacity B per track and the data transfer speed S are fixed in the floppy disc drive, and the operating system operates under the fixed condition. Accordingly, the total memory capacity M on one side of the disc is conventionally increased by increasing the number A of tracks used on one side of the disc, that is, by increasing the track density D. The total memory capacity of the Winchester disc is conventionally increased similarly.
Hence, in order to improve the linear recording density (bit/inch) of the disc, the minimum usable radius on the disc is reduced by downsizing the disc. Thus, in addition to the 8-inch disc, smaller discs such as the 5.25-inch, 3.5-inch, and 3-inch discs have been developed. As a result, the increase in the total memory capacity M on one side of the disc is not perfectly proportional to the improvement in the track density and the linear recording density.
Description will now be given for a case where a linear recording density which is N times that of the conventional disc is to be obtained, where N is an integer greater than one. When it is assumed that the size of the disc is identical to that of the conventional 5.25-inch disc and the data transfer speed S is the same as that of the conventional 5.25-inch disc, the memory capacity B per track becomes equal to 4.times.N (kilobytes). Accordingly, when the track density D and the number A of tracks on one side of the disc are identical to those of the conventional disc, the total memory capacity M on one side of the disc becomes equal to 4.times.N.times.A (kilobytes) from the equation (2), and the total memory capacity M on one side of this disc becomes N times that of the conventional 5.25-inch disc. However, the memory capacity B per track of this disc also becomes N times that of the conventional 5.25-inch disc, and the digital signals reproduced from this disc cannot be processed by use of the conventional (existing) operating system. In other words, in order to record and reproduce the digital signal on the disc with a high density, the memory capacity B per track, the data transfer speed S and the like must be changed, and the operating system must be changed accordingly. Therefore, the above disc for high density recording and reproduction uses a recording format completely different from the existing recording format, and the disc is only playable on a recording and reproducing apparatus which employs the new system. For this reason, there is a problem in that such a disc for high density recording and reproduction is not compatible with the recording and reproducing apparatus employing the existing system.